Herein the term “photopatternable film” refers to materials that can be patterned onto localized domains on a surface through the use of a light to alter the material properties. Exposure to light initiates processes that create a difference in the solubility of the material between those domains that have been exposed to light and those domains that have not be exposed to light. After exposing selected domains to light, solvents are used to remove either those domains not exposed to light, leaving patterned localized areas consisting of those domains that were exposed to light; or alternatively, the material may have been designed so that the domains exposed to light are removed through solvent action while those domains not exposed to light remain. The solvent action is used to develop the pattern in the film that was uniform prior to exposure to light.
The term “sorbent film means films made from a material that will absorb chemical species that diffuse through the film material upon exposure to those species.
The term “functionalized means that the film has interactive properties due to chemical structural units in the film, and these interactive properties make the film suitable for particular applications, e.g. microanalytical materials and devices such as chemical sensors.
The term “chemically selective” means that the film will absorb some chemical species more than other chemical species, and thus be selective for those species that are more strongly absorbed. Chemical selectivity is important in the suitability of the film for particular applications, e.g. microanalytical applications such as chemical sensors.
A precusor molecule may be a monomer, an oligomer, a polymer, or a crosslinker that is incorporated in the composition.
Chemically selective sorbent films can be designed to be selective for some species relative to others through the incorporation of chemical structural units that provide articular interactive properties.
There exists a need for chemically interactive sorbent materials and formulations that can be patterned on devices and structures. There is also a need for a method to provide sorbent materials that have a specific chemical interactions required for their microanalytical function in their particular applications and which can be patterned on device structures. There is further a need to be able to create a variety of such materials and formulations so that each has different chemically interactive properties but each can be patterned into localized domains on device structures.
A principal object of the present invention is to use hydrosilylation chemistry to crosslink polymeric films where they have been exposed to light. The crosslinked areas then have different solubility in developing solvents than do uncrosslinked areas. The developing solvent is used to remove the unexposed, uncrosslinked regions of the film, leaving the exposed, crosslinked regions of the film. Hydrosilylation chemistry is useful for this purpose because it is selective. A variety of materials can be crosslinked by use of this chemistry while leaving other chemical materials unaffected. Another object of the invention is to use hydrosilylation chemistry to convert monomers and oligomers to polymeric films where they have been exposed to light. Another object is to crosslink the polymeric film as it is forming from the monomers and oligomers provided in the film composition.
Another object of the invention is to graft the sorbent film onto a surface at the same time that it is crosslinked and/or polymerized. An object of the invention is to use a hydrosilylation catalyst that is inactive until it is exposed to light. Once it is activated by light, it initiates hydrosilylation reactions within the film that polymerize, crosslink and/or graft the film. A further object of the invention is to use polymer or prepolymer formulations on surfaces that have been modified so that grafting can occur and to use the catalyst to also initiate the grafting process. A further object of the invention is develop combinations of precursor molecules that, when incorporated into the composition and exposed to light of a type and in a sufficient amount, will react by hydrosilylation to create a sorbent film that will selectively absorb chemical species when exposed to those chemical species. It is necessary that the precursor molecules be miscible in order to react in the composition. Therefore it is an object of the invention to prepare combinations of precursor molecules that are miscible and will react to create the chemically selective sorbent film. It is a further object of the invention to combine a functionalized monomer with an oligomer that is derived from the same monomer. This approach where both the monomer and the oligomer are derived from the same molecule assures that these two precursor molecules will be miscible with one another in a film. Thus a monomer with two carbon—carbon multiple bonds may be combined with an oligomer derived from the reaction of the same monomer with an excess of an alpha,omega-dihydrooligodimethylsiloxane to create an oligomer that contains the monomer and which is terminated in silicon hydride bonds.
The following patents and publications should be carefully considered for the purpose of putting the present invention into proper perspective relative to the prior art: U.S. Pat. No. 5,145,886, granted Sep. 8, 1992, to Joel D. Oxman and Larry D. Boardman; U.S. Pat. No. 6,015,869, granted Jan. 18, 2000, to Jay W. Grate and Steven N. Kaganove; PCT Application No. WO 92/10529, filed by the Minnesota Mining And Manufacturing Company, U.S.A., and published on Jun. 25, 1992; PCT Application No. WO 92/10544, filed by Minnesota Mining And Manufacturing Company, and published on Jun. 25, 1992; and publication: Fredrick. D. Lewis and Gwen D. Salvi, “Platinum (II) Bis(β-diketonates) as Photoactivated Hydrosilation Catalysts, Inorganic Chemistry”, 1995, 34, 3182–3189; Bryan E. Fry and D. C. Neckers, “Rapid Photoactivated Hydrosilation Polymerization of Vinyldimethlysilane”, Macromolecules 1996, 29, 5306–5312; Bryan E. Fry, Andrew Guo, D. C. Neckers, “Photoactivated Hydrosilation Curing of a Ceramic Precursor: Crosslinking and Pyrolysis of branched oligo [(methylsilylene)methylene], Journal of Organiometallic Chemistry 538 (1997), 151–161; and Andrew Guo, Bryan E. Fry and Douglas C. Neckeres, “Highly Active Visible-Light Photo-catalysts for Curing a Ceramic Precursor”, Chemistry Materials, 1998, 10, 531–536.